Penicillin derivative



United States Patent 3,250,679 PENICILLIN DERIVATIVE Alexander ll. A.Jansen, Petersfield, and Trevor J. Russell,

Bracklesham Bay, Sussex, England, assignors to American Home ProductsCorporation, New York, N.Y., a corporation of Delaware N Drawing. FiledMay 27, 1964, Ser. No. 370,687 Claims priority, application GreatBritain, May 30, 1963, 21,7 50/ 63 3 Claims. (Cl. 167-65) This inventionrelates to a new-penicillin derivative, a process for preparing it, andpharmaceutical preparations containing it.

Free penicillins and their salts are generally less effective when takenorally than when administered parenterally, because of inactivation inthe stomach and gut; higher doses are required to achieve the same bloodlevels, and there is a great variation in the ability of individuals toabsorb penicillin into the blood by theoral route. Thus, benzylpenicillin (Penicillin G) is much less effective as an antibiotic agentwhen administered orally than when it is administered parenterally. Muchresearch has in the past been directed to the discovery of penicillinswhich are less readily inactivated in the stomach and gut so that arelatively large part of the therapeutic agent administered orally canbe absorbed into the blood. This has led to the development of some morehighly orally-active penicillins, for example phenoxymethyl penicillin(Penicillin V), which is comparatively stable to hydrochloric acid inthe stomach. Nevertheless, even with Penicillin V absorption is stillerratic. Moreover, this antibiotic is less potent against manypathogenic bacteria than is benzyl penicillin.

When a penicillin arrives in the blood stream, whether by the oral orthe parenteral route, some is broken down and the rest is excretedbefore inactivation. A dose of a sodium penicillin is normallycompletely eliminated from the body within a few hours of intramuscularinjection.

The concentration of the penicillin in the blood steadily decreases fromits maximum level, and the penicillin may require replenishment byfrequent repeated further administration in order to maintain asuflicient concentration until the presence of the therapeutic agent isno longer required. Accordingly research has in the past also beendirected to the provision of long-acting preparations which releasetheir penicillin content in such a way as to maintain a relatively highconcentration of the therapeutic agent in the blood over a prolongedperiod. Thus, attempts have been made to solve this problem by means ofpenicillin salts or other derivatives from which the penicillin ischemically released in the body. As a result some long-acting injectablepreparations have been developed, but no derivatives have hitherto beenfound which can be used orally to give a sustained high blood level ofantibiotic. It has in practice proved extremely difficultto find Iderivatives which will break down to release the free penicillin whereit is required if breakdown in the stomach is to be avoided. Forexample, many penicillin esters show no substantial therapeutic activityin man, as their hydrolysis to free penicillin in the body proceeds fartoo slowly.

The present invention is concerned with a new penicillin derivativewhich, although of no practical value for parenteral use, behaves onoral administration consistent with it being resistant to breakdown inthe stomach but sus ceptible to break-down beyond the stomach and insuch a way that free penicillin appears in the blood stream over aprolonged period. That these properties are remarkable is emphasized bythe fact that of many closely related compounds which have been made andtested, it is the only one to possess these properties to a significantextent. The reason for this is obscure, but it may be that its chemicaland physical properties, including size and shape of the molecule,uniquely fit the requirements for stability in the stomach andsubsequent enzymic hydrolysis. The uniqueness of this behavior is shownby the fact that the properties are lost not only on variation of thenature of the derivative group but also on variation of the penicillinon which the derivative is based.

The penicillin derivative of the invention is acetoxymethylbenzylpenicillinate, having the structure:

It is to be noted that because the compound of the invention is aderivative of Penicillin G, it has a much wider spectrum of antibioticactivity than such penicillins as Penicillin V which are particularlyfavored for their good oral absorption.

A process for preparing the penicillin derivative of the invention isone in which an acetoxymethyl halide is caused to condense withbenzylpenicillin, which in practice is in the form of a salt. Suitablebenzylpenicillin salts are alkali metal and amine salts, for examplesodium, potassium, diethylamine, and triethylamine salts. Theacetoxymethyl halide is preferably the bromide, but can also be thechloride. These acetoxymethyl halides can be prepared by the reaction ofthe corresponding acetyl halide with paraformaldehyde by heating thereagents together in the presence of anhydrous zinc chloride, andsubsequently isolating the acetoxymethyl halide by distillation.

The preparation of the derivative of the invention is convenientlycarried out by bringing the acetoxymethyl halide into contact with thepenicillin salt in an inertsolvent at a temperature within the range offrom 0 to 30 amide, which, preferably, should be as dry as possible inorder to avoid side-reactions with water which reduce the yield ofproduct. After the reagents have been allowed sufiicient time to react,the product is conveniently poured into water (preferably buffered at pHand the precipitate of penicillin derivative filtered off. Thederivative can then be taken up in a suitable organic solvent, forexample chloroform or isopropyl alcohol, and isolated in crystallineform. As is well understood in the art of penicillin manufacture, thepreparation of the therapeutic agentin crystalline form is important,and preferably the penicillin, derivative of this invention is obtainedin crystalline form, M.P. 1068 C., [a] +l54.

The pharmaceutical preparations of the invention are ones for oral usecomprising acetoxymethyl benzylpenicillinate in association with apharmaceutically acceptable carrier suitable for oral administration. I

The pharmaceutically acceptable carrier can be either solid or liquid.Solid form preparations include powders, tablets, dispersible granules,capsules, troches and cachets. A solid carrier can be one or moresubstances which may also act as flavoring agents, solubilizers,lubricants, suspending agents, binders, or tablet-disintegrating agents;it can also be an encapsulating material. In powders, the carrier is afinely divided solid, which is in'admixture with the finely dividedcompound. In tablets the compound is mixed with carrier having thenecessary binding properties in suitable proportions and compacted inthe shape and size desired. The powders and tablets preferably containfrom about 5 to 99% of the active ingredient. Suitable solid carriersare magnesium carbonate, magnesium stearate, talc, sugar, lactose,pictin, dextrin, starch, gelatinytragacanth, methyl cellulose, andsodium carboxymethyl cellulose. The term preparation is intended toinclude the formulation of the compound with encapsulating material ascarrier, providing a capsule in which the compound (with or withoutother carriers) is surrounded by carrier, which is thus in associationwith it. Similarly, cachets are included. Liquid form preparationsinclude solutions, suspensions, and emulsions. Aqueous suspensionssuitable for oral use can be made by dispersing the finely dividedcompound in water with sodium carboxymet-hyl cellulose as suspendingagent. Oily suspensions can be prepared by dispersing the finely-dividedcompound in 'arachis oil. The pharmaceutical preparation may alsocontain other active ingredients, for example, other penicillinantibiotics.

Preferably the pharmaceutical preparation is in unit dosage form. Insuch :form, the preparation is subdivided in unit does containingappropriate quantities of the compound. The unit dosage form can be apackaged preparation, the package containing discrete quantities ofpreparation, for example, packeted powders. The unit dosage form can bea capsule, cachet or tablet itself, or it can be the appropriate numberof any of these in packaged form. A unit dose of the preparation maycontain between 40 and 1200 mg, 'and preferably from 150 to 800 mg, ofthe penicillin derivative of the invention.

The invention includes a product in which a penicillin derivative of theinvention is brought into association with a pharmaceutically acceptablecarrier to give a preparation of the invention. The penicillinderivative and prodnets of the invention are useful in the curative orprophylactic treatment of mammals, especially human beings, sufferingfrom, or liable to sufier from, infection by pathogenic bacteriasensitive to benzyl-penicillin, by orally administering to such a mammala pharmaceutical preparation in accordance with the invention. In humansa unit dose need only be administered 3 or 4 times every 24 hours forthe maintenance of effective concentrations of antibiotic in the blood,whereas the recommended fre quency of dosage using potassium PenicillinV is once every 4 hours.

The invention is illustrated by the following examples, in whichinfrared absorption data (IR) refer to the positions of maxima given incmr Example I A mixture of triethylammonium beuzylpenicillinate (2.6 g.,the triethylammonium salt of Penicillin G),

bromomethyl acetate (4.5 cc.) and dimethylformamide cc.) was shakenovernight at room temperature and.

Example II Dimethylfornramide (22 kg., containing less than 0.05 ofwater) and dry potassium benzylpenicillinate (10 kg.) were charged intoa reaction vessel and cooled to 10 C.

Bromomethyl acetate (4.15 kg.) was added to the stirred solution over aperiod of 1 hour, whilemaintaining the temperature at below 15 C., andthe stirring was continued for a fiurther 6 hours at 10-l5 C.

The reaction mixture was then added during 1 hour to a pH 6 buffersolution prepared from water 1.), potassium dihydrogen phosphate (280g.) and dipotasslum hydrogen phosphate (720 g), the mixture beingstirred vigorously and cooled to 5 C. After a further hours stirring,the precipitated white solid was collected by filtration and washed withwater (5 1.). The washed product was dissolved in boiling isopropylalcohol (14 1.), the solution cooled to 15 C., and the recrystallizedproduct collected and dried at 40-5 C. in vacuo to give acetoxyrnethyllbenzyl-penicillinate (9.1 kg, 83% of theory), M.P. 106'8; [a] +154 (1%in chloroform.)

Example III Powdered acetoxymethyl benzylpenicillina-te (250 parts byweight), maize starch (66 parts), purified wood cellulose powder (30parts) and magnesium 'stearate (3 parts) are mixed together, the mixturepassed through a 40 mesh British Standard sieve and slugged twice,granulated and passed through a 16 mesh British sieve. With theresulting granules there is mixed further magnesium stearate (1 part)and the mixture is then compressed in a tabletting machine, to givetablets of 350 mg. weight.

Example IV Acetoxymethyl benzylpenicillinate is dissolved inpolyethylene glycol of molecular weight 400 and the resulting solutiondiluted [with the solvent in such a way that the final solution contains100 rug/cc. of the penicillin derivative. A suitable unit dose of theresulting liquid preparation of the invention is 5 cc.

Example V Solid crystalline acetoxymethyl benzylpenicillinate is filledinto gelatin capsules in quantities of 360 mg. per capsule, to give asolid preparation of the invention with the gelatin acting aspharmaceutical carrier.

The advantages of the invention are further illustrated by the followingtest results.

Example VI A blood sample of each of 8 dogs (beagles) was tested forcontrol purposes to show it had no activity as assayed by the cup-platemethod of penicillin bioassay using the organism Sarcimz lutea.

Acetoxymethyl benzylpenicillinate was administered by mouth to thefasted dogs using capsular preparations similar to those described inExample V above, except that the amount of penicillin derivative in eachcapsule was varied in such a way as to give a unit dose in singlecapsule of 20 mg. of penicillin derivative per kg. of body weight toeach dog.

After definite intervals a sample of each dogs blood was taken and theserum submitted to bioassay, the results being compared with thoseobtained using potassium TAB LE A Serum penicillin in pgJCC.

Compound Hours after oral administration Acetoxyrnet-hylbenzylpenicillinate 0. 90 0. 71 0. 36 0. 11 0. 05 0. 01 PotassiumPenicillin G 3.9 3. 92 0.6 0. 06 0 0 0 Potassium Penicillin V 0. 83 0.56 0. 11 0. 0. 02 O 0 Benzathine Penicillin G 0. 32 0. 28 0. 03 0 0 0 0Phenethicillin 1. 11 0. 7 0. l4 0. O2 0. O2 0 0 Phenbencillim- 0. 90 0.75 0. 06 0. 02 0. 02 0 0 Ampicillin 2. 44 2. 02 0. 57 0. 04 0.01 0 0Example VII orally in a unit dose of 750 mg. to fasted human patients ain the form of the preparation of Example II above. Blood samples weretaken and submitted to penicillin bioassay before ingestion (ascontrols, showing no antibiotic activity) and at intervals up to 10hours from administration. In a series of 16 patients, 14 achieved bloodserum levels bioassayed as Penicillin G of over 1.0 ,ug./cc. during the2 hours after administration, 14 had blood serum levels of over 0.1lg/cc. after 6 hours or later, and all of 5 TABLE B Penicillin in gJg.wet weight Spleen Kidney Liver Lung Heart Skeletal Ileum Bile muscleAcetoxymethyl benzyl penieil1inate 0. 47 2. 4 0. 90 0.37 0. 47 0. 170.60 18. 2 Potassium Penicillin G 0.03 0.75 0.50 0.23 0.07 0 0. 23 15. 3

Example VIII TABLE C Basie compounds and derivatives tested patientstested after 10 hours had blood serum levels of over 0.05 ag/cc.

We claim:

1. Acetoxymethyl benzylpenicillinate.

2. The method of preparing acetoxymethyl benzylpenicillinate whichcomprises: condensing an acetoxyrnethyl halide with a salt ofbenzylpenicillin selected from the group consisting of the alkali metaland amine salts thereof, in an inert solvent at a temperature within therange of from 0 to 30 C.

3. A pharmaceutical preparation in unit dosage form suitable for oraluse and comprising a therapeutic amount Serum penicillin in gJce.

Hours after oral administration a-Phenoxyethyl penicillin(Phenethieillin) Acetoxymethyl PropionoxymethyL (Phenbencillin) xymethyl3-0-Chlorophenyl-5-methy1-4-isoxazolyl penicillin (Cloxacillin):

Acetoxymethyl Butyryloxymethyl.

The compound of the invention has been administered of crystallineacetoxymethyl benzylpenicillinate and a pharmaceutically acceptablecarrier.

No references cited.

HENRY R. JILES, Acting Primary Examiner.

5 JAMES W. ADAMS, JR., Assistant Examiner.

3. A PHARMACEUTICAL PREPARATION IN UNIT DOSAGE FORM SUITABLE FOR ORALUSE AND COMPRISING A THERAPEUTIC AMOUNT OF CRYSTALLINE ACETOXYMETHYLBENZYLPENICILLINATE AND A PHARMACEUTICALLY ACCEPTABLE CARRIER.